Solar-Terrestrial Physics Solar-Terrestrial Physics Solar-Terrestrial Physics 2500-0535 103586 10.12737/stp-113202506 20TH ANNUAL CONFERENCE “PLASMA PHYSICS IN THE SOLAR SYSTEM”. FEBRUARY 10–14, 2025, SPACE RESEARCH INSTITUTE RAS, MOSCOW, RUSSIA 20TH ANNUAL CONFERENCE “PLASMA PHYSICS IN THE SOLAR SYSTEM”. FEBRUARY 10–14, 2025, SPACE RESEARCH INSTITUTE RAS, MOSCOW, RUSSIA 20TH ANNUAL CONFERENCE “PLASMA PHYSICS IN THE SOLAR SYSTEM”. FEBRUARY 10–14, 2025, SPACE RESEARCH INSTITUTE RAS, MOSCOW, RUSSIA Studying dynamics of energy spectrum of solar diurnal variations in cosmic rays during solar activity cycles 20–25, using method of crossed muon telescopes Studying dynamics of energy spectrum of solar diurnal variations in cosmic rays during solar activity cycles 20–25, using method of crossed muon telescopes https://orcid.org/0000-0003-2184-8089 Гололобов Петр Юрьевич Gololobov Peter Yur'evich gpeter@ikfia.sbras.ru https://orcid.org/0000-0002-1348-4708 Григорьев Владислав Георгиевич Grigoryev Vladislav Georgievich grig@ikfia.ysn.ru

кандидат физико-математических наук;

candidate of physical and mathematical sciences;

 https://orcid.org/0000-0003-1247-4513 Герасимова Сардаана Кимовна Gerasimova Sardaana Kimovna danagsk@mail.ru

кандидат физико-математических наук;

candidate of physical and mathematical sciences;

 Институт космофизических исследований и аэрономии им. Ю.Г. Шафера СО РАН Якутск Россия Yu.G. Shafer Institute of Cosmophysical Research and Aeronomy SB RAS Yakutsk Russian Federation Институт космофизических исследований и аэрономии им. Ю.Г. Шафера СО РАН Якутск Россия Yu.G. Shafer Institute of Cosmophysical Research and Aeronomy SB RAS Yakutsk Russian Federation Институт космофизических исследований и аэрономии им. Ю.Г. Шафера СО РАН Якутск Россия Yu.G. Shafer Institute of Cosmophysical Research and Aeronomy SB RAS Yakutsk Russian Federation 22 09 2025 22 09 2025 11 3 44 49 10 03 2025 27 05 2025 https://naukaru.ru/en/nauka/article/103586/view

The cosmic ray (CR) intensity recorded by ground-based detectors experiences solar diurnal variations (SDVs) associated with the existence of anisotropic angular distribution of CRs in near-Earth space. Long-term observations show that SDVs exhibit a dependence on the solar activity cycle, experiencing periodic 11- and 22-year variations. Such behavior of SDVs is linked to a change in the nature of galactic CR propagation in the heliosphere when it changes during a solar activity cycle. On the other hand, this phenomenon can be partially due to a change in the magnitude of CR drift by the geomagnetic field associated with changes in the SDV energy spectrum. In this work, we determine the dynamics of the SDV energy spectrum in solar activity cycles. The solution to this problem presents certain difficulties associated with peculiarities of ground-based CR recording and with the sensitivity of CR detectors to changes in the state of environment. Therefore, we employ an approach using crossed muon telescopes to estimate it, which allows us to bypass the above difficulties. We analyze data from Yakutsk, Nagoya, Sao Martinho, and Hobart muon telescopes for 1972–2022. It is shown that at solar minima during periods of positive polarity of the Sun's general magnetic field, a significant softening of the spectrum is observed. The results are discussed.

The cosmic ray (CR) intensity recorded by ground-based detectors experiences solar diurnal variations (SDVs) associated with the existence of anisotropic angular distribution of CRs in near-Earth space. Long-term observations show that SDVs exhibit a dependence on the solar activity cycle, experiencing periodic 11- and 22-year variations. Such behavior of SDVs is linked to a change in the nature of galactic CR propagation in the heliosphere when it changes during a solar activity cycle. On the other hand, this phenomenon can be partially due to a change in the magnitude of CR drift by the geomagnetic field associated with changes in the SDV energy spectrum. In this work, we determine the dynamics of the SDV energy spectrum in solar activity cycles. The solution to this problem presents certain difficulties associated with peculiarities of ground-based CR recording and with the sensitivity of CR detectors to changes in the state of environment. Therefore, we employ an approach using crossed muon telescopes to estimate it, which allows us to bypass the above difficulties. We analyze data from Yakutsk, Nagoya, Sao Martinho, and Hobart muon telescopes for 1972–2022. It is shown that at solar minima during periods of positive polarity of the Sun's general magnetic field, a significant softening of the spectrum is observed. The results are discussed.

 cosmic rays solar diurnal variation energy spectrum muon telescope. cosmic rays solar diurnal variation energy spectrum muon telescope. The work was carried out pursuant to Government assignment of the Ministry of Science and Higher Education of the Russian Federation (Theme No. FWRS-2021-0012) The work was carried out pursuant to Government assignment of the Ministry of Science and Higher Education of the Russian Federation (Theme No. FWRS-2021-0012)

Ahluwalia H.S. A correlation between IMF and the limiting primary rigidity for cosmic ray diurnal anisotropy. Geophys. Res. Lett. 1992, vol. 19, iss. 6, pp. 633–636. DOI: 10.1029/92GL00525. Ahluwalia H.S. A correlation between IMF and the limiting primary rigidity for cosmic ray diurnal anisotropy. Geophys. Res. Lett. 1992, vol. 19, iss. 6, pp. 633–636. DOI: 10.1029/92GL00525. Ahluwalia H.S., Sabbah I.S. The limiting primary rigidity of cosmic ray diurnal anisotropy. Planet. Space Sci. 1993, vol. 41, iss. 2, pp. 105–112. DOI: 10.1016/0032-0633(93)90038-4. Ahluwalia H.S., Sabbah I.S. The limiting primary rigidity of cosmic ray diurnal anisotropy. Planet. Space Sci. 1993, vol. 41, iss. 2, pp. 105–112. DOI: 10.1016/0032-0633(93)90038-4. Berkova M.D., Grigoryev V.G., Preobrazhensky M.S., Zverev A.S., Yanke V.G. Temperature effect observed for the muon component in the Yakutsk cosmic-ray spectrograph. Physics of Atomic Nuclei. 2018, vol. 81, no. 6, pp. 742–751. DOI: 10.1134/S1063778818050046. Berkova M.D., Grigoryev V.G., Preobrazhensky M.S., Zverev A.S., Yanke V.G. Temperature effect observed for the muon component in the Yakutsk cosmic-ray spectrograph. Physics of Atomic Nuclei. 2018, vol. 81, no. 6, pp. 742–751. DOI: 10.1134/S1063778818050046. Chuprova V.P., Gerasimova S.K., Grigoryev V.G., Krivoshapkin P.A., Krymsky G.F., Mamrukova V.P., et al. The brief history of experimental research of cosmic ray variations in Yakutia, Adv. Space Res. 2009, vol. 44, iss. 10., pp. 1200–1206. DOI: 10.1016/j.asr.2008.12.024. Chuprova V.P., Gerasimova S.K., Grigoryev V.G., Krivoshapkin P.A., Krymsky G.F., Mamrukova V.P., et al. The brief history of experimental research of cosmic ray variations in Yakutia, Adv. Space Res. 2009, vol. 44, iss. 10., pp. 1200–1206. DOI: 10.1016/j.asr.2008.12.024. Dorman L.I. Variatsii kosmicheskikh luchey [Variations of Cosmic Rays]. Moscow: Gosudarstvennoe izdatel’stvo tekhniko-teoreticheskoi literatury (State Publishing House of Technical and Theoretical Literature), 1957, 492 p. (In Russian). Dorman L.I. Variatsii kosmicheskikh luchey [Variations of Cosmic Rays]. Moscow: Gosudarstvennoe izdatel’stvo tekhniko-teoreticheskoi literatury (State Publishing House of Technical and Theoretical Literature), 1957, 492 p. (In Russian). Dorman L.I., Smirnov V.S., Tyasto M.I. Kosmicheskie luchi v magnitnom pole Zemli [Cosmic Rays in the Earth's Magnetic Field]. Moscow: Nauka (Science), 1971, 400 p. (In Russian). Dorman L.I., Smirnov V.S., Tyasto M.I. Kosmicheskie luchi v magnitnom pole Zemli [Cosmic Rays in the Earth's Magnetic Field]. Moscow: Nauka (Science), 1971, 400 p. (In Russian). Fujimoto K., Inoue A., Murakami K., Nagashima K. Coupling coefficients of cosmic ray daily variation for meson telescopes. Report of Cosmic-Ray Research Lab. Nagoya University. 1984, no. 9. Fujimoto K., Inoue A., Murakami K., Nagashima K. Coupling coefficients of cosmic ray daily variation for meson telescopes. Report of Cosmic-Ray Research Lab. Nagoya University. 1984, no. 9. Gerasimova S.K., Gololobov P.Yu., Grigoryev V.G., Krivoshapkin P., Krymsky G., Starodubtsev S. Heliospheric modulation of cosmic rays: model and observation. Sol.-Terr. Phys. 2017, vol. 3, iss. 1, pp. 78–102. DOI: 10.12737/article_58f970f2455545.93154609. Gerasimova S.K., Gololobov P.Yu., Grigoryev V.G., Krivoshapkin P., Krymsky G., Starodubtsev S. Heliospheric modulation of cosmic rays: model and observation. Sol.-Terr. Phys. 2017, vol. 3, iss. 1, pp. 78–102. DOI: 10.12737/article_58f970f2455545.93154609. Gololobov P.Yu., Krivoshapkin P.A., Krymsky G.F., Gerasimova S.K. Investigating the influence of geometry of the heliospheric neutral current sheet and solar activity on modulation of galactic cosmic rays with a method of main components. Sol.-Terr. Phys. 2020, vol. 6, iss. 1, pp. 24–28. DOI: 10.12737/stp-61202002. Gololobov P.Yu., Krivoshapkin P.A., Krymsky G.F., Gerasimova S.K. Investigating the influence of geometry of the heliospheric neutral current sheet and solar activity on modulation of galactic cosmic rays with a method of main components. Sol.-Terr. Phys. 2020, vol. 6, iss. 1, pp. 24–28. DOI: 10.12737/stp-61202002. Hall D.L., Duldig M.L., Humble J.E. Cosmic-ray modulation parameters derived from the solar diurnal variation. Astrophys. J. 1997, vol. 482, pp. 1038–1049. DOI: 10.1086/304158. Hall D.L., Duldig M.L., Humble J.E. Cosmic-ray modulation parameters derived from the solar diurnal variation. Astrophys. J. 1997, vol. 482, pp. 1038–1049. DOI: 10.1086/304158. Kóta J., Munakata K., Yasue S., Kato C., Mori S. The origin of solar diurnal variation of galactic cosmic rays above 100 GV. Proc. 30th ICRC. 2008, vol. 1, pp. 589–592. Kóta J., Munakata K., Yasue S., Kato C., Mori S. The origin of solar diurnal variation of galactic cosmic rays above 100 GV. Proc. 30th ICRC. 2008, vol. 1, pp. 589–592. Krymsky G.F., Kuzmin A.I., Chirkov N.P. Distribution of cosmic rays and detector response vectors. I. Geomagnetizm i aeronomiya [Geomagnetism and Aeronomy]. 1966, vol. 6, iss. 6, pp. 991–996. (In Russian). Krymsky G.F., Kuzmin A.I., Chirkov N.P. Distribution of cosmic rays and detector response vectors. I. Geomagnetizm i aeronomiya [Geomagnetism and Aeronomy]. 1966, vol. 6, iss. 6, pp. 991–996. (In Russian). Krymsky G.F., Kuzmin A.I., Chirkov N.P., et al. Distribution of cosmic rays and detector response vectors. II. Geomagnetizm i aeronomiya [Geomagnetism and Aeronomy]. 1967, vol. 7, iss. 1, pp. 11–15. (In Russian). Krymsky G.F., Kuzmin A.I., Chirkov N.P., et al. Distribution of cosmic rays and detector response vectors. II. Geomagnetizm i aeronomiya [Geomagnetism and Aeronomy]. 1967, vol. 7, iss. 1, pp. 11–15. (In Russian). Munakata K., Mizoguchi Y., Kato C., Yasue S., Mori S., Takita M., Kóta J. Solar cycle dependence of the diurnal anisotropy of 0.6 TeV cosmic-ray intensity observed with the Matsushiro underground muon detector. Astrophys. J. 2010, vol. 712, pp. 1100–1106. DOI: 10.1088/0004-637X/712/2/1100. Munakata K., Mizoguchi Y., Kato C., Yasue S., Mori S., Takita M., Kóta J. Solar cycle dependence of the diurnal anisotropy of 0.6 TeV cosmic-ray intensity observed with the Matsushiro underground muon detector. Astrophys. J. 2010, vol. 712, pp. 1100–1106. DOI: 10.1088/0004-637X/712/2/1100. Nikolashkin S.V., Titov S.V., Gololobov P.Yu. The effect of winter stratospheric warmings on the intensity of the muon component of secondary cosmic rays. Proc. 26th International Symposium on Atmospheric and Ocean Optics. Atmospheric Physics. 2020, vol. 11560. DOI: 10.1117/12.2575697. Nikolashkin S.V., Titov S.V., Gololobov P.Yu. The effect of winter stratospheric warmings on the intensity of the muon component of secondary cosmic rays. Proc. 26th International Symposium on Atmospheric and Ocean Optics. Atmospheric Physics. 2020, vol. 11560. DOI: 10.1117/12.2575697. Okazaki Y., Fushishita A., Narumi T., Kato C., Yasue S., Kuwabara T., et al. Drift effects and the cosmic ray density gradient in a solar rotation period: first observation with the Global Muon Detector Network (GMDN). Astrophys. J. 2008, vol. 681, pp. 693–707. DOI: 10.1086/588277. Okazaki Y., Fushishita A., Narumi T., Kato C., Yasue S., Kuwabara T., et al. Drift effects and the cosmic ray density gradient in a solar rotation period: first observation with the Global Muon Detector Network (GMDN). Astrophys. J. 2008, vol. 681, pp. 693–707. DOI: 10.1086/588277. Pomerantz M.A., Duggal S.P. The cosmic ray solar diurnal anisotropy. Space Sci. Rev. 1971, vol. 12, pp. 75–130. DOI: 10.1007/BF00172130. Pomerantz M.A., Duggal S.P. The cosmic ray solar diurnal anisotropy. Space Sci. Rev. 1971, vol. 12, pp. 75–130. DOI: 10.1007/BF00172130. Rao U.R., McCracken K.G., Venkatesan D. Asymptotic cones of acceptance and their use in the study of the daily variation of cosmic ray radiation. J. Geophys. Res. 1963, vol. 68, iss. 2, pp. 345–369. DOI: 10.1029/JZ068i002p00345. Rao U.R., McCracken K.G., Venkatesan D. Asymptotic cones of acceptance and their use in the study of the daily variation of cosmic ray radiation. J. Geophys. Res. 1963, vol. 68, iss. 2, pp. 345–369. DOI: 10.1029/JZ068i002p00345. Riker J.F., Ahluwalia H.S., Sabbah I.S. The limiting primary rigidities for the cosmic ray diurnal anisotropy during a solar magnetic cycle. EOS: Trans. Am. Geophys. Union. 1989, vol. 70, 1256. Riker J.F., Ahluwalia H.S., Sabbah I.S. The limiting primary rigidities for the cosmic ray diurnal anisotropy during a solar magnetic cycle. EOS: Trans. Am. Geophys. Union. 1989, vol. 70, 1256. Sabbah I. Solar magnetic polarity dependency of the cosmic ray diurnal variation. J. Geophys. Res: Space Phys. 2013, vol. 118, pp. 4739–4747. DOI: 10.1002/jgra.50431. Sabbah I. Solar magnetic polarity dependency of the cosmic ray diurnal variation. J. Geophys. Res: Space Phys. 2013, vol. 118, pp. 4739–4747. DOI: 10.1002/jgra.50431. Skripin G.V. Issledovanie anizotropii kosmicheskikh luchey metodom skreshchennykh teleskopov [Study of the anisotropy of cosmic rays using the crossed telescopes method]. Cand. of Phys. and Math. Sci. diss. Yakutsk, 1965, 184 p. (In Russian). Skripin G.V. Issledovanie anizotropii kosmicheskikh luchey metodom skreshchennykh teleskopov [Study of the anisotropy of cosmic rays using the crossed telescopes method]. Cand. of Phys. and Math. Sci. diss. Yakutsk, 1965, 184 p. (In Russian). Skripin G.V., Krivoshapkin P.A., Krymsky G.F., Filippov V.A. Study of cosmic ray anisotropy using the crossed telescopes method. Geomagnetizm i aeronomiya [Geomagnetism and Aeronomy]. 1965, vol. 5, iss. 5, pp. 817–822. (In Russian). Skripin G.V., Krivoshapkin P.A., Krymsky G.F., Filippov V.A. Study of cosmic ray anisotropy using the crossed telescopes method. Geomagnetizm i aeronomiya [Geomagnetism and Aeronomy]. 1965, vol. 5, iss. 5, pp. 817–822. (In Russian). URL: https://cosray.shinshu-u.ac.jp/crest/DB/Public/main.php (accessed March 7, 2025). URL: https://cosray.shinshu-u.ac.jp/crest/DB/Public/main.php (accessed March 7, 2025). URL: https://ysn.ru/ipm/ (accessed March 7, 2025). URL: https://ysn.ru/ipm/ (accessed March 7, 2025). URL: http://hdl.handle.net/10091/0002001448 (accessed March 7, 2025). URL: http://hdl.handle.net/10091/0002001448 (accessed March 7, 2025).